This invention relates to gas drying. More particularly, it relates to inhibiting the formation and deposition of solids from used desiccant solutions.
Moisture is commonly removed from natural gas in gas transmission lines by passing the gas through a gas dryer which holds a bed of desiccant tablets. As the desiccant tablets pick up moisture, a solution is formed of the desiccant salts. The solution drains into a sump area from which it is removed, usually by periodic draining.
A problem exists with such dryers and desiccants, in that the generally highly concentrated solutions of desiccant salts which drain into the sump tend to crystallize or otherwise come out of solution, and remain in the sump when the solution is drained or otherwise removed. In the quiescent sump, the solidified salts resist redissolving, and tend to build up over time, occupying sump volume and necessitating frequent manual removal. Gas transmission lines and dryers are placed and used throughout a wide variety of climatic and seasonal conditions, and, although the problem of solids formation is probably more acute in locations where temperatures are lowest, it presents itself even in warmer climates because the salts will come out of solution in the cooler or colder evening and night temperatures.
A possible remedy for the problem would be to provide a heater for the sump solution, but this is not economically desirable.
We have invented a method of inhibiting solids formation in solutions of used desiccant salts which comprises conveying the heat of hydration from the desiccant bed to the solution of used desiccant salts in a sump. The heat of hydration may be transported in any feasible manner, but we prefer to use either a heat exchange fluid in an enclosure, or a heat conductor in the form of rods. Optionally, we may agitate the solution in the sump. For example, the force of the gas flow in the dryer may be used to turn mixing blades in the sump.
We use the term xe2x80x9cheat of hydrationxe2x80x9d herein to include heat of solution.